Process for producing wet ribavirin pellets

ABSTRACT

A process for producing wet ribavirin pellets is provided in order to make pharmaceutical dosages of ribavirin. The process is particularly useful as an alternative method for preparing pharmaceutical dosages of ribavirin that reduces the amount of ribavirin dust that is produced during the manufacturing process and allows for greater control of dissolution rates. According to the preferred embodiments, this method is accomplished through mixing ribavirin with at least one excipient into a uniform mixture, forming the mixture into a granulated mass by adding a wetting agent, shaping said granulated mass into soluble particles and drying the flowable particles. The process enables Ribavirin pharmaceutical pellets to be mixed with a binder and disintegrant to form a uniform mixture.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a process for making oral pharmaceutical dosages of ribavirin. More specifically, the drug ribavirin is a synthetic nucleoside analog with broad spectrum antiviral activity. Ribavirin is one of a combination of drugs being administered to patients with Hepatitis C and other viral infections.

[0003] Ribavirin is currently manufactured, among other methods, using a process commonly called dry compaction. Dry compaction utilizes high pressure to form a ribbon of ribavirin that is subsequently reduced to a free flowing powder by milling. The undesirable side effects of manufacturing ribavirin by dry compaction include the creation of excessive dust, a potential health hazard, as well as the risk that high pressure, which can produce high heat, could produce polymorphic forms. Different polymorphs or combinations of polymorphs are undesirable because they can sometimes change the manner in which the active drug moiety is absorbed.

[0004] The present invention describes a method for manufacturing ribavirin using a wet granulation process. This process forms a free flowing ribavirin by mixing ribavirin with a wetting agent and various excipients to form a granulation that can be extruded and spheronized, producing a pellet. This process is not only an alternative method for producing ribavirin, but also offers several advantages over the dry compaction process. One advantage of wet granulation is that significantly less dust is produced, which is important from a health and safety standpoint. Another advantage of the present invention is that wet granulation allows for greater control of dissolution rates. In addition, this wet granulation method results in the ribavirin having better flow characteristics, enabling faster encapsulation and lower weight variations. Finally, because there is little heat or excessive pressure, the wet granulation method lowers the risk of creating polymorphs and, therefore, allows for greater uniformity of the crystalline structure.

[0005] 2. Description of the Prior Art

[0006] It is well known in the art that a raw drug often is unsuitable for medicinal purposes because the raw drug has undesirable dissolution profiles and cannot be efficiently encapsulated because of poor flow qualities. For efficient encapsulation, proper flow is vital to producing a uniform, quality pharmaceutical product for a variety of reasons, including that these factors can affect how much active drug is absorbed and when it is absorbed into the human body.

[0007] Excipients are often added to raw drugs in order to create a mixture having improved flow, compaction, or disintegration characteristics. These excipients can add various qualities either to the end product or to some stage of the manufacturing process. Common excipients include disintegrants, lubricants, fillers, binders and wetting agents. Disintegrants absorb water quickly when the dosage form reaches the alimentary canal. Lubricants help with mold release and flow. Fillers provide bulk and, along with binders and wetting agents, add adhesion to the mixture. However, some formulas produce a finished dosage form that is too large or results in disintegration rates which could be slower or faster than is optimal.

[0008] The following three methods are commonly used to mix excipients with raw drugs to produce pharmaceutical capsules: (1) direct blend, (2) dry compaction, and (3) wet granulation. In the direct blend process, drugs and selected excipients are added to a blender and mixed in the dry state to produce a uniform distribution of the active drug. This direct blend method requires an active drug with acceptable flow characteristics. In the dry compaction process, drugs and selected excipients are mixed and then compacted into a ribbon and milled to a uniform particle size. This operation often generates heat. The result is a free flowing powder that can be encapsulated. Finally, in the wet granulation process, the drugs are mixed either in their liquid form or with a wetting agent to produce a wet mass that can be further processed to produce a free flowing material, which in turn can be encapsulated.

[0009] Heretofore, there have been no references in the prior art that demonstrate the successful use of the wet granulation process to manufacture ribavirin capsules. Rather ribavirin is presently made using a dry compaction process as shown in U.S. Pat. Nos. 6,051,252, 5,196,594 and 5,914,128. Each of U.S. Pat. Nos. 6,051,252, 5,196,594 and 5,914,128 describes a method of producing dosages of ribavirin using high pressures which could generate high temperatures. Specifically, U.S. Pat. Nos. 6,051,252 and 5,914,128 both describe the use of 0.10 compressing forces that range from 50 to 75 kilonewtons of force.

[0010] Although the most common pharmaceutical dosage of ribavirin is 200 mg, other dosages could be manufactured.

SUMMARY OF THE INVENTION

[0011] It is, therefore, an object of the present invention to provide an alternative method for preparing pharmaceutical dosages of ribavirin which reduces the amount of ribavirin dust that is produced during the manufacturing process, allows for greater control of dissolution rates, and increases flow rates. This goal is accomplished through a wet granulation process that combines ribavirin with specific disintegrants, binders, fillers, and wetting agents in sufficient quantities to form an extrudable mass.

[0012] One preferred embodiment of the invention teaches that the extrudable mass is mixed to form a uniform mixture of active drug and excipients, which mixture is subsequently formed into pellets by extrusion and spheronization.

[0013] More specifically, the present invention is a process for producing ribavirin pellets, comprising the steps of mixing ribavirin with at least one excipient into a uniform mixture; forming said uniform mixture into a granulated mass by adding a wetting agent to said uniform mixture; shaping said granulated mass into flowable particles; and drying said flowable particles, resulting in dried flowable particles.

[0014] These objects, as well as other objects and advantages of the present invention, will become apparent from the following description, in reference to the illustrations and charts appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a better understanding of the invention, refer to the accompanying chart in which FIG. 1 is an electronic photograph of pellets produced by the preferred embodiment enlarged at a ratio of 1:1000.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention discloses a process for making pharmaceutical dosages of ribavirin through wet granulation. There are several formulas that can be utilized to produce ribavirin pellets by wet granulation, preferably with extrusion and spheronization. TABLE 1 % Range of Formulation Ingredient Total Formulation Function in the Formulation ribavirin 31-35 Active Pharmaceutical Ingredient microcrystalline cellulose   27-35.5 Binder/Diluent croscarmellose sodium 0-3 Disintegrant polyethylene glycol 11-39 Binder/Wetting Agent

[0017] Under one of the preferred embodiments, the dry ingredients listed in Table 1 above are mixed together and granulated with the wetting agent, extruded through a screen (0.4 millimeter (“mm”) to 1.0 mm), spheronized, and fluid bed dried. Depending on the dosage required, the resulting pellets are filled into hard gelatin capsules sizes “1” to “00”. TABLE 2 % Range of Function in Formulation Ingredient Total Formulation the Formulation ribavirin, U.S. Pharmaceutical 41-67 Active Pharmaceutical Grade (“USP”) Ingredient microcrystalline cellulose 24-33 Binder/Diluent croscarmellose sodium 2-6 Disintegrant polyethylene glycol  5-17 Binder/Wetting Agent povidone   1-4.5 Binder water USP 15-30 Wetting Agent (calculated on a wet basis)

[0018] Under another preferred embodiment, the dry ingredients listed in Table 2 above are mixed together and granulated with the wetting agent, extruded through a screen (0.4 mm to 1.0 mm), spheronized, and fluid bed dried. Depending on the dosage required, the resulting pellets are filled into hard gelatin capsules sizes “1” to “00”. TABLE 3 % Range of Function in Formulation Ingredient Total Formulation the Formulation ribavirin USP 41-67 Active Pharmaceutical Ingredient microcrystalline cellulose 24-33 Binder/Diluent croscarmellose sodium 2-6 Disintegrant povidone   1-4.5 Binder lactose  5-10 Diluent water USP 15-79 Wetting Agent (calculated on a wet basis)

[0019] Under another preferred embodiment, the dry ingredients listed in the Table 3 above are mixed together and granulated with the wetting agent, extruded through a screen (0.4 mm-1.0 mm), spheronized, and fluid bed dried. Depending on the dosage required, the resulting pellets are filled into hard gelatin capsules sizes “1” to “00”.

[0020] One of the preferred embodiments results in a product that is encapsulated in size “1” or “1el” (elongated) capsules to form a 200 milligram (“mg”) dose of active ribavirin. The total capsule weight is approximately 270 mg. One of the preferred embodiments also calls for a 200 mg pharmaceutical dosage in which at least 90% of the ribavirin dissolves within 30 minutes. Thus, although the method described in the claims can be used to produce ribavirin in different sized capsules or having different dissolution rates, this disclosure will only provide the detailed weights and other measurements that will result in a capsule containing 200 mg of active ribavirin having the previously mentioned rate of dissolution.

[0021] In the aforesaid preferred embodiment, the following formulation and material quantities are used most preferably: TABLE 4 kilogram (“kg”)/ kg/ kg/ kg/ 10,000 10,000 1,000,000 1,000,000 Capsules Capsules Capsules Capsules % of mg/ 200 mg 300 mg 200 mg 400 mg Ingredient Formulation Capsule (size 1 el) (size 0) (size 1 el) (size 00) ribavirin USP 74 200 2 3 200 400 microcrystalline 15.6 42 0.42 0.63 42 84 cellulose croscarmellose 3.7 10 0.1 0.15 10 20 sodium povidone 1.1 3 0.03 0.045 3 6 lactose 5.6 15 0.15 0.23 15 30 water USP 1.75 2.63 165 330 Total 100 270 2.7 4.05 270 540 Total with Water USP 4.45 6.68 435 870 % Water USP in 39 39 38 38 the wet granulation

[0022] Ribavirin USP is mixed for 3 to 15 minutes along with microcrystalline cellulose, lactose monohydrate, croscarmellose sodium and povidone K 27-33 in a suitably sized granulator. Purified water USP is added to the mixture at a rate of 2 kg to 50 kg per minute. The wet mass is granulated for an additional 30 seconds to 20 minutes (depending on batch size).

[0023] After granulating, the wet mass is fed into an extruder at a rate that avoids product stagnation and excessive accumulation. The extruded mass is spheronized on an appropriately sized marumerizer or equivalent equipment using typical parameters. Typical parameters used during said spheronization include those listed as follows: Jacket water temperature  45-60° C. Groove plate configuration Medium Marumerizer speed setting 0.5-1.0 Spherionization time 0.5-2 minute/portion

[0024] In the aforesaid preferred embodiment, the pellets are fluid-bed dried.

[0025] Drying is continued until the pellets having a loss on drying (LOD) of not more than 5% and not less than 0.5% is achieved. Following drying, the pellets are sieved by use of a 16 mesh or 18 mesh screen.

[0026] After the pellets are sieved, said pellets can be used to fill a capsule employing standard encapsulators. In this preferred embodiment, the capsule is a size 1 elongated capsule which will have a desired total capsule fill weight of 270 mg.

[0027] Said preferred embodiment produces a dosage in which at least 90% will dissolve in 30 minutes. However, it is anticipated within this application that future uses of ribavirin may lead to a demand for ribavirin dosages having a different dissolution profile. Therefore, this invention discloses and claims the addition of coatings to the dried pellets to yield other dissolution profiles. Coatings in common use include polymethacrylic, dyethyl-aminophyl, polyethanene glycols and other excipients well known in the art. 

We claim:
 1. A process for producing ribavirin pellets, comprising the steps of: mixing ribavirin with at least one excipient into a uniform mixture; forming said uniform mixture into a granulated mass by adding a wetting agent to said uniform mixture; shaping said granulated mass into flowable particles; and drying said flowable particles.
 2. A process according to claim 1, wherein said excipient is povidone, starch, lactose, polyethylene glycol, and hydroxy propylmethyl cellulose.
 3. A process according to claim 1, wherein said excipient is selected from a group consisting of croscarmellose sodium, starch, cellulose, bentonite, and cross-povidones.
 4. A process according to claim 1, wherein said wetting agent consists of purified water USP.
 5. A process according to claim 1, wherein a filler is added to the ribavirin.
 6. A process according to claim 5, wherein said filler is selected from a group consisting of microcrystalline cellulose, lactose, sucrose, cellulose and starch.
 7. A process according to claim 5, wherein said step of mixing is accomplished by adding said filler in accordance with said uniform mixture, resulting in said uniform mixture consisting of ingredients containing between 40% and 50% filler by weight.
 8. A process according to claim 1, wherein said step of mixing is accomplished by adding excipient, resulting in said uniform mixture consisting of ingredients containing from 1% to 9% excipient by weight.
 9. A process according to claim 1, wherein said step of mixing is accomplished by adding said ribavirin, resulting in said uniform mixture consisting of ingredients containing between 35% to 80% ribavirin by weight.
 10. A process according to claim 1, wherein achievement of a granulated mass is accomplished by said step of mixing until a smooth granulated mass is formed.
 11. A process according to claim 1, wherein said step of shaping is accomplished by a further step of spheronizing said granulated mass until uniform sized pellets are produced.
 12. A process according to claim 11, wherein said step of shaping is accomplished by said step of spheronizing said granulated mass until said uniform sized pellets are produced and by a further step of extruding said uniform sized pellets through a screen whereby said screen ranges in size from a 0.40 mm screen to a 1.0 mm screen.
 13. A process according to claim 1, wherein said step of drying is accomplished through a further step of heating said mixture to a temperature ranging from 35° Celsius to 45° Celsius, until said mixture contains a moisture content ranging from 0.5% to 5.0%.
 14. A process according to claim 1, wherein a capsule is filled with said dried flowable particles.
 15. A process for producing ribavirin pharmaceutical pellets, comprising the steps of: mixing said ribavirin USP with a filler, a disintegrant and a lubricant resulting in a mixture containing a range from 40% to 50% of said filler by weight, a range from 1% to 9% of said disintegrant by weight and a range from 35% to 80% of said ribavirin by weight; adding sufficient wetting agent to said mixture, resulting in the formation of an extrudable mass; shaping said extrudable mass into pellets; and drying said pellets.
 16. A process according to claim 15, wherein said filler is selected from the group consisting of microcrystalline cellulose, lactose, sucrose, cellulose and starch.
 17. A process according to claim 15, wherein said disintegrant is a selected from a group consisting of croscarmellose sodium, starch, cellulose and bentonite.
 18. A process according to claim 15, wherein said step of shaping is accomplished by a further step of spheronizing said extruded mass until a uniform size of said pellets is produced.
 19. A process according to claim 15, wherein said step of shaping is accomplished by a further step of spheronizing said extrudable mass until a uniform size of pellets is produced and a further step of extruding said pellets through a screen, whereby said screen ranges in size from a 0.40 mm screen to a 1.0 mm screen.
 20. A process according to claim 15, wherein said step of drying is accomplished by a further step of heating said mixture to a temperature ranging from 35° Celsius to 45° Celsius until said mixture produces a moisture content ranging from 0.5% and 5.0%.
 21. A process according to claim 15, wherein a size “1” capsule is completely filled with said dried pellets such that the filled capsule is produced containing a range of 180 mg to 220 mg of said ribavirin, resulting in said size 1 capsule and having a total weight ranging from 243 mg to 297 mg.
 22. A process according to claim 15, wherein a size “1el” capsule is completely filled with said dried pellets such that the filled capsule is produced containing a range of 180 mg to 220 mg of said ribavirin, resulting in said size 1el capsule and having a total weight ranging from 243 mg to 297 mg.
 23. A process according to claim 15, wherein a size “0” capsule is completely filled with said dried pellets such that the filled capsule is produced containing a range of 270 mg to 330 mg of said ribavirin, resulting in said size 0 capsule and having a total weight ranging from 364 mg to 446 mg.
 24. A process according to claim 15, wherein a size “00” capsule is completely filled with said dried pellets such that the filled capsule is produced containing a range of 360 mg to 440 mg of said ribavirin, resulting in said size 00 capsule and having a total weight ranging from 486 mg to 594 mg.
 25. A process for producing ribavirin pharmaceutical pellets comprising the steps of: mixing said ribavirin pharmaceutical pellets with microcrystalline cellulose, resulting in said ribavirin and said microcrystalline cellulose forming a mixture containing a range of from 40% to 50% of said microcyrstalline cellulose by weight and a range of from 35% to 80% of said ribavirin by weight; adding sufficient croscarmellose sodium to said mixture such that the mixed ingredients contain a range from 1% to 9% croscarmellose sodium by weight; forming said mixed ingredients into an extrudable mass by adding water; shaping said extrudable mass into pellets; drying said pellets to produce dried pellets; and filling capsules with said dried pellets.
 26. A process according to claim 25, wherein said step of shaping is accomplished by a further step of spherionizing said extrudable mass, resulting in a production of uniform sized pellets.
 27. A process of claim 26, wherein said step of shaping is accomplished by a further step of extruding said pellets through a screen ranging from a 0.40 mm screen to a 1.0 mm screen.
 28. A process according to claim 25, wherein said screen is sized between 0.4 mm and 1.0 mm.
 29. A process according to claim 25, wherein said step of drying is accomplished through heating of said mixed ingredients to a temperature ranging from 35° Celsius to 45° Celsius until said mixed ingredients contain a moisture content ranging from 0.5% to 5.0%.
 30. A process according to claim 25, wherein a size “1” of said capsules is completely filled, resulting in said pellets containing a total weight ranging from 243 mg to 297 mg.
 31. A process according to claim 25, wherein a size “1el” of said capsules is completely filled, resulting in said pellets containing a total weight ranging from 243 mg to 297 mg.
 32. A process according to claim 25, wherein a size “0” of said capsules is completely filled, resulting in said pellets containing a total weight ranging from 364 mg to 446 mg.
 33. A process according to claim 25, wherein a size “00” of said capsules is completely filled, resulting in said pellets containing a total weight ranging from 486 mg to 594 mg.
 34. A process according to claim 1, wherein at least 90% of said ribavirin dissolves in 30 minutes.
 35. A process according to claim 15, wherein at least 90% of said ribavirin dissolves in 30 minutes.
 36. A process according to claim 1, wherein a coating is added to said dried pellets on an outside surface before encapsulation, resulting in a decreased rate of release during a given time span in comparison to said release under a condition without said coating.
 37. A process according to claim 15, wherein a coating is added to said dried pellets on an outside surface before encapsulation, resulting in a decreased rate of release during a given time span in comparison to said release under a condition without said coating.
 38. A process according to claim 25, wherein a coating is added to said dried pellets on an outside surface before encapsulation, resulting in a decreased rate of release during a given time span in comparison to said release under a condition without said coating. 